Systems and methods for performing storage operations using network attached storage

ABSTRACT

Systems and methods for performing hierarchical storage operations on electronic data in a computer network are provided. In one embodiment, the present invention may store electronic data from a network device to a network attached storage (NAS) device pursuant to certain storage criteria. The data stored on the NAS may be migrated to a secondary storage and a stub file having a pointer pointing to the secondary storage may be put at the location the data was previously stored on the NAS. The stub file may redirect the network device to the secondary storage if a read request for the data is received from the network device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/293,975, filed Nov. 10, 2011, entitled SYSTEMS AND METHODS FORPERFORMING STORAGE OPERATIONS USING NETWORK ATTACHED STORAGE, which is acontinuation of U.S. application Ser. No. 12/467,596, filed May 18,2009, entitled SYSTEMS AND METHODS FOR PERFORMING STORAGE OPERATIONSUSING NETWORK ATTACHED STORAGE, now U.S. Pat. No. 8,078,583, issued Dec.13, 2011, which is a division of U.S. application Ser. No. 10/990,360,filed Nov. 15, 2004, entitled SYSTEMS AND METHODS FOR PERFORMING STORAGEOPERATIONS USING NETWORK ATTACHED STORAGE, now U.S. Pat. No. 7,546,324,issued Jun. 9, 2009, which claims the benefit of U.S. Provisional PatentApplication No. 60/519,949, filed Nov. 13, 2003, entitled PERFORMINGSTORAGE OPERATIONS USING NETWORK ATTACHED STORAGE, each of which ishereby incorporated herein by reference in its entirety.

COPYRIGHT NOTICE

Portion of the disclosure of this patent document contains material thatis subject to copyright protection. The copyright owner has no objectionto the facsimile reproduction by anyone of the patent document or thepatent disclosures, as it appears in the Patent and Trademark Officepatent files or records, but otherwise expressly reserves all otherrights to copyright protection.

RELATED APPLICATIONS

This application is related to the following patents and pendingapplications, each of which is hereby incorporated herein by referencein its entirety:

U.S. Pat. No. 6,418,478, titled PIPELINED HIGH SPEED DATA TRANSFERMECHANISM, issued Jul. 9, 2002;

U.S. application Ser. No. 09/610,738, titled MODULAR BACKUP ANDRETRIEVAL SYSTEM USED IN CONJUNCTION WITH A STORAGE AREA NETWORK, filedJul. 6, 2000, now U.S. Pat. No. 7,035,880, issued Apr. 25, 2006;

U.S. Pat. No. 6,542,972, titled LOGICAL VIEW AND ACCESS TO PHYSICALSTORAGE IN MODULAR DATA AND STORAGE MANAGEMENT SYSTEM, issued Apr. 1,2003;

U.S. application Ser. No. 10/658,095, titled DYNAMIC STORAGE DEVICEPOOLING IN A COMPUTER SYSTEM, filed Sep. 9, 2003, now U.S. Pat. No.7,130,970, issued Oct. 31, 2006; and

U.S. application Ser. No. 10/818,749, titled SYSTEM AND METHOD FORPERFORMING STORAGE OPERATIONS IN A COMPUTER NETWORK, filed Apr. 3, 2004,now U.S. Pat. No. 7,246,207, issued Jul. 17, 2007.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates generally to performing storage operationson electronic data in a computer network, and more particularly, to datastorage systems that employ primary and secondary storage deviceswherein certain electronic data from the primary storage device isrelocated to the secondary storage device pursuant to a storage policyand electronic data from the second storage device may retrieveddirectly or through the primary storage device.

The storage of electronic data has evolved over time. During the earlydevelopment of the computer, storage of electronic data was limited toindividual computers. Electronic data was stored in the Random AccessMemory (RAM) or some other storage medium such as a magnetic tape orhard drive that was a part of the computer itself.

Later, with the advent of network computing, the storage of electronicdata gradually migrated from the individual computer to stand-alonestorage devices accessible via a network. These individual networkstorage devices soon evolved into networked tape drives, opticallibraries, Redundant Arrays of Inexpensive Disks (RAID), CD-ROMjukeboxes, and other devices. Common architectures also include networkattached storage devices (NAS devices) that are coupled to a particularnetwork (or networks) that are used to provide dedicated storage forvarious storage operations that may be required by a particular network(e.g., backup operations, archiving, and other storage operationsincluding the management and retrieval of such information).

A NAS device may include a specialized file server or network attachedstorage system that connects to the network. A NAS device often containsa reduced capacity or minimized operating and file management system(e.g., a microkernel) and normally processes only input/output (I/O)requests by supporting common file sharing protocols such as the Unixnetwork file system (NFS), DOS/Windows, and server message block/commonInternet file system (SMB/CIFS). Using traditional local area networkprotocols such as Ethernet and transmission control protocol/internetprotocol (TCP/IP), a NAS device typically enables additional storage tobe quickly added by connecting to a network hub or switch.

Hierarchical storage management (HSM) provides for the automaticmovement of files from hard disk to slower, less-expensive storagemedia, or secondary storage. As shown in FIG. 1, the typical migrationhierarchy is from magnetic disk 10 to optical disk 20 to tape 30.Conventional HSM software usually monitors hard disk capacity and movesdata from one storage level to the next (e.g., from production level toprimary storage and/or from primary storage to secondary storage, etc.)based on storage criteria associated with that data such as a storagepolicy, age, category or other criteria as specified by the network orsystem administrator. For example, an email system such as MicrosoftOutlook™ may have attachments “aged off” (i.e., migrated once an agerequirement is met) from production level storage to a network attachedstorage device By HSM systems. When data is moved off the hard disk, itis typically replaced with a smaller “placeholder” or “stub” file thatindicates, among other things, where the original file is located on thesecondary storage device.

A stub file may contain some basic information to identify the fileitself and also include information indicating the location of the dataon the secondary storage device. When the stub file is accessed with theintention of performing a certain storage operation, such as a read orwrite operation, the file system call (or a read/write request) istrapped by software and a data retrieval process (sometimes referred toas de-migration or restore) is completed prior to satisfying therequest. De-migration is often accomplished by inserting specializedsoftware into the I/O stack to intercept read/write requests. The datais usually copied back to the original primary storage location fromsecondary storage, and then the read/write request is processed as ifthe file had not been moved. The effect is that the user sees andmanipulates the file as the user normally would, except experiencing asmall latency initially when the de-migration occurs.

Currently, however, HSM is not commonly practiced in NAS devices. Onereason for this is because it is very difficult, if not impossible, tointercept file system calls in NAS devices. Moreover, there are manydifferent types of NAS devices, such as WAFL by Network Appliance ofSunnyvale, Calif., the EMC Celera file system by the EMC Corporation ofHopkinton, Mass., the Netware file system by Novell of Provo, Utah, andother vendors. Most of these systems export their file systems to hostcomputers such as the common Internet file system (CIFS) or the networkfile system (NFS), but provide no mechanism to run software on theiroperating systems or reside on the file system stack to interceptread/write or other data requests. Further, many NAS devices areproprietary, which may require a significant reverse-engineering effortto determine how to insert software into the I/O stack to perform HSMoperations, reducing portability of an HSM implementation.

Accordingly, what is needed are systems and methods that overcome theseand other deficiencies.

SUMMARY OF THE INVENTION

The present invention provides, among other things, systems and methodsfor performing storage operations for electronic data in a computernetwork on a network attached storage device (NAS). Some of the stepsinvolved in one aspect of the invention may include receiving electronicdata from a network device for writing to the NAS device; writing theelectronic data to the NAS device in a first location (i.e., primarystorage); subsequently storing the electronic data to a second location(i.e., secondary storage); and storing a stub file at the firstlocation, the stub file including a pointer to the second location thatmay redirect the network device to the second location if an accessrequest for the electronic data is received from the network device. Insome embodiments, when the NAS device receives an electronic datarequest from a network device, the operating system of the networkdevice may recognize the stub file as a stub file. In this case, thenetwork device may use the pointer to find the actual location of thestored electronic data, where the electronic data may be accessed andprocessed over the network by the network device itself.

In accordance with some aspects of the present invention, computerizedmethods are provided for archiving data that is written to a firstlocation in a NAS device to a second location, and storing a stub fileat the first location, the stub file having a pointer pointing to thesecond location, the stub file for redirecting a network device to thesecond location if a read request for the file is received from thenetwork device.

The system may include a NAS device connected to a network. The networkmay interconnect several network devices, including, for example,several client computers, host computers, server computers, mainframecomputers or mid-range computers, all sending file system requests tothe NAS. The NAS device may receive the file request from the networkdevices and process them.

An example of a method for processing a request for storing data on theNAS device may include receiving the data from a network device forwriting to the NAS device; writing the data to the NAS device in a firstlocation known to the network device; storing the data to a secondlocation; and storing a stub file at the first location, the stub filehaving a pointer pointing to the second location, the stub file forredirecting the network device to the second location if a read requestfor the data is received from the network device. In some embodiments,the stub file may be named the same as the data that was stored in thefirst location before archiving. However, when the network attachedstorage device provides a read request to read the data, the operatingsystem of the network device may recognize the stub file as a stub file.The network device may then perform the task of following the pointer tothe actual location of the archived data, where the data may be readfrom and processed over the network by the network device itself. Thisrelieves the NAS device from excess processing of the read request,including having to de-migrate the data from secondary storage.

Thus, one way to process a read request in accordance with an embodimentof the present invention includes opening the stub file stored in placeof the data by the NAS device at a first location, the first locationbeing where the data was stored before the file was archived to a secondlocation by the network attached storage system; reading a pointerstored in the stub file, the pointer pointing to the second location;and reading the data from the second storage location.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated in the figures of the accompanying drawingswhich are meant to be exemplary and not limiting, in which likereferences are intended to refer to like or corresponding partsthroughout, and in which:

FIG. 1 is a diagrammatic representation of basic components and dataflow of prior art HSM systems;

FIG. 2 is a block diagram of a system constructed in accordance with theprinciples of the present invention for storing and retrievingelectronic data from primary and secondary storage locations;

FIG. 3 is a flow chart illustrating some of the steps for performingstorage and retrieval operations on electronic data in a computernetwork according to an embodiment of the invention;

FIG. 4 is a flow chart illustrating some of the steps performed when asystem application attempts to access electronic data moved from primarystorage to secondary storage in accordance with an embodiment of thepresent invention;

FIG. 5 is a flow chart illustrating some of the steps performed when asystem application attempts to alter electronic data moved from primarystorage to secondary storage in accordance with an embodiment of thepresent invention; and

FIG. 6 is a chart illustrating steps performed in a Solaris-basedembodiment of the system shown in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of a system 50 constructed in accordance with theprinciples of the present invention is shown in FIG. 2. As shown, system50 may include a NAS device 100, a network 90, network devices 85, datamigrators 95, primary storage device 102, secondary storage devices 120and 130, storage area network (SAN) 70, media agent 97, storage device140 and storage manager 180. NAS 100 may be coupled to network 90 whichmay itself also include or be part of several other network types,including, without limitation, Ethernet, IP, Infineon, Wi-Fi, wireless,Bluetooth or token-ring, and other types.

One or more network devices 85 may be coupled to network 90. Eachnetwork device 85 may include a client application, a client computer, ahost computer, a mainframe computer, a mid-range computer, or any othertype of device capable of being connected in a network and runningapplications which produce electronic data that is periodically stored.Such data may be sometimes referred to as “production level” data. Insome embodiments, a network device 85 may have the ability to generateelectronic data requests, such as file requests and system requests toNAS device 100 through the network 90.

NAS device 100 may include, and/or be connected to, a primary storagedevice 102 such as a hard disk or other memory that provides relativelyhigh-speed data access (as compared to secondary storage systems).Primary storage device 102 may include additional storage for NAS device100 (which may itself include some internal storage), and may be thefirst network storage device accessed by network devices 85.

As shown in FIG. 2, NAS device 100 may include one or more datamigrators 95, each of which may be implemented as a software programoperating on NAS 100, as an external computer connected to NAS 100, orany combination of the two implementations. Data migrator 95 may beresponsible for storing electronic data generated by a network device 85in primary storage device 102, or other memory location in NAS device100, based on a set of storage criteria specified by a system user(e.g., storage policy, file size, age, type, etc.). Moreover, datamigrators 95 may form a list or otherwise keep track of all qualifyingdata within network devices 85 and copy that data to primary storagedevice 102 as necessary (e.g., in a backup or archiving procedure,discussed in more detail below).

A storage policy (or criteria) is generally a data structure or otherinformation that includes a set of preferences and other storagecriteria for performing a storage operation. The preferences and storagecriteria may include, but are not limited to: a storage location,relationships between system components, network pathway(s) to utilize,retention policies, data characteristics, compression or encryptionrequirements, preferred system components to utilize in a storageoperation, and other criteria relating to a storage operation. A storagepolicy may be stored to a storage manager index, to archive media asmetadata for use in restore operations or other storage operations, orto other locations or components of the system.

Storage operations, which may generally include data migration andarchiving operations may involve some or all of the followingoperations, but are not limited thereto, including creation, storage,retrieval, migration, deletion, and tracking of primary or productionvolume data, secondary volume data, primary copies, secondary copies,auxiliary copies, snapshot copies, backup copies, incremental copies,differential copies, synthetic copies, HSM copies, archive copies,Information Lifecycle Management (“mM”) copies, and other types ofcopies and versions of electronic data.

De-migration as used herein generally refers to data retrieval-typeoperations and may occur when electronic data that has been previouslytransferred from a first location to a second location is transferredback or otherwise restored to the first location. For example, datastored on NAS 100 and migrated to in secondary storage and then returnedto NAS 100 may be considered de-migrated. De-migration may also occur inother contexts, for example, when data is migrated from one tier ofstorage to another tier of storage (e.g., from RAID storage to tapestorage) based on aging policies in an ILM context, etc. Thus, if it wasdesired to access data that had been migrated to a tape, that data couldbe de-migrated from the tape back to RAID, etc.

In some embodiments, data migrators 95 may also monitor or otherwisekeep track of electronic data stored in primary storage 102 for possiblearchiving in secondary storage devices 120 and 130. In such embodiments,some or all data migrators 95 may periodically scan primary storagedevice 102 searching for data that meet a set storage or archivingcriteria. If certain data on device 102 satisfies a set of establishedarchiving criteria, data migrator 95 may “discover” certain informationregarding that data and then migrate it (i.e., coordinate the transferthe data or compressed versions of the data) to secondary storagedevices, which may include tape libraries, magnetic media, opticalmedia, or other storage devices. Moreover, is some embodiments archivingcriteria, which generally may be a subset set of storage criteria (orpolicies), may specify criteria for archiving data or for moving datafrom primary to secondary storage devices.

As shown in FIG. 2, one or more secondary storage devices 120 and 130may be coupled to NAS device 100 and/or to one or more stand alone orexternal versions of data migrators 95. Each secondary storage device120 and 130 may include some type of mass storage device that istypically used for archiving or storing large volumes of data. Whether afile is stored to secondary storage device 120 or device 130 may dependon several different factors, for example, on the set of storagecriteria, the size of the data, the space available on each storagedevice, etc.

In some embodiments, data migrators 95 may generally communicate withthe secondary storage devices 120 and 130 via a local bus such as a SCSIadaptor or an HBA (host bus adaptor). In some embodiments, secondarystorage devices 120 and 130 may be communicatively coupled to the NASdevice 100 or data migrators 95 via a storage area network (SAN) 70.

Certain hardware and software elements of system 50 may be the same asthose described in the three-tier backup system commercially availableas the CommVault QiNetx backup system from CommVault Systems, Inc. ofOceanport, N.J., and further described in application Ser. No.09/610,738 which is incorporated herein by reference in its entirety.

In some embodiments, rather than using a dedicated SAN 70 to connect NAS100 to secondary storage devices 120 and 130, the secondary storagedevices may be directly connected to the network 90. In this case, thedata migrators 95 may store or archive the files over the network 90directly to the secondary storage devices 120 and 130. In the case wherestand-alone versions of the data migrators 95 are used without adedicated SAN 70, data migrators 95 may be connected to the network 90,with each stand-alone data migrator 95 performing its tasks on the NASdevice 100 over the network.

In some embodiments, system 50 may include a storage manager 180 and oneor more of the following: a media agent 98, an index cache 97, andanother information storage device 140 that may be a redundant array ofindependent disks (RAID) or other storage system. These elements areexemplary of a three-tier backup system such as the CommVault QiNetxbackup system, available from CommVault Systems, Inc. of Oceanport,N.J., and further described in application Ser. No. 09/610,738 which isincorporated herein by reference in its entirety.

Storage manager 180 may generally be a software module or applicationthat coordinates and controls system 50. Storage manager 180 maycommunicate with some or all elements of system 50 including clientnetwork devices 85, media agents 97, and storage devices 120, 130 and140, to initiate and manage system storage operations, backups,migrations, and recoveries.

A media agent 97 may generally be a software module that conveys data,as directed by the storage manager 180, between network device 85, datamigrator 95, and one or more of the secondary storage devices 120, 130and 140 as necessary. Media agent 97 is coupled to and may control thesecondary storage devices 120, 130 and 140 and may communicate with thestorage devices 120, 130 and 140 either via a local bus such as a SCSIadaptor, an HBA or SAN 70.

Each media agent 97 may maintain an index cache 98 that stores indexdata system 50 generates during, store backup, migration, archive andrestore operations. For example, storage operations for MicrosoftExchange data may generate index data. Such index data may providesystem 50 with an efficient mechanism for locating stored data forrecovery or restore operations. This index data is generally stored withthe data backed up on storage devices 120, 130 and 140 as a header fileor other local indicia and media agent 97 (that typically controls astorage operation) may also write an additional copy of the index datato its index cache 98. The data in the media agent index cache 98 isthus generally readily available to system 50 for use in storageoperations and other activities without having to be first retrievedfrom a storage device 120, 130 or 140.

Storage manager 180 may also maintain an index cache 98. The index datamay be used to indicate logical associations between components of thesystem, user preferences, management tasks, and other useful data. Forexample, the storage manager 180 may use its index cache 98 to tracklogical associations between several media agents 97 and storage devices120, 130 and 140.

Index caches 98 may reside on their corresponding storage component'shard disk or other fixed storage device. In one embodiment, system 50may manage index cache 98 on a least recently used (“LRU”) basis asknown in the art. When the capacity of the index cache 98 is reached,system 50 may overwrite those files in the index cache 98 that have beenleast recently accessed with new index data. In some embodiments, beforedata in the index cache 98 is overwritten, the data may be copied t astorage device 120, 130 or 140 as a “cache copy.” If a recoveryoperation requires data that is no longer stored in the index cache 98,such as in the case of a cache miss, system 50 may recover the indexdata from the index cache copy stored in the storage device 120, 130 or140.

In some embodiments, other components of system 50 may reside andexecute on the storage manager 180. For example, one or more datamigrators 95 may execute on the storage manager 180.

Referring now to FIG. 3, some of the steps involved in practicing anembodiment of the present invention are shown in the flow chartillustrated thereon. When a network device sends a write request forwriting a data to the NAS device, the write request may include afolder, directory or other location in which to store the data on theNAS device (step 300). Through a network, the network device may writethe data to the NAS device, storing the file in primary storage (and/orNAS) in the location specified in the write request (step 302). Asshown, after a data migrator copies data to secondary storage (step 304)the data migrator may store a stub file at the original file location,the stub file having a pointer pointing to the location in secondarystorage where the actual file was stored, and to which the networkdevice can be redirected if a read request for the file is received fromthe network device, step 306.

Referring now to FIG. 4, some of the steps involved in attempting toread certain data that has been migrated to secondary storage media isshown in the flow chart of FIG. 4. As illustrated, a network device mayattempt to read data that was originally stored at the current locationof the stub file at step 400. The operating system of the network devicemay read the stub file at step 402 and recognize that the data is now astub file, and be automatically redirected to read the data from thelocation pointed to by the stub file at step 404. This may beaccomplished for example, by having the network device follow a Windowsshortcut or a UNIX softlink (in Solaris applications). The data may thenbe accessed by directly reading from the secondary storage location atstep 406. Although this process may cause a slight delay or latencyattributable to the redirection, and, in the case of a secondary storagedevice using cassettes or other library media, may cause additionaldelay involved with finding the proper media, the delay normallyassociated with de-migrating the data to primary storage is eliminated.

With reference to FIG. 5, a flow chart illustrating some of the stepsperformed when data is edited after being read from archive by a clientnetwork device are shown. After the data is read from a secondarystorage device and edited (step 500), if the network device performs asave operation and issues a write request to the NAS device (andgenerally speaking, not a save-as operation to store the file in a newlocation), the data may be stored in the primary storage device at theoriginal location where the data was stored before archiving, replacingthe stub file (step 502). Depending on the type of file system andconfiguration of the secondary storage device, the archived data may bemarked as deleted or outdated if the secondary storage device retainsold copies of files as a backup mechanism (step 504). Next, the editeddata continues to reside in primary storage until a data migratorarchives the edited data to secondary storage (step 506) and places astub file in its place in primary storage (step 508).

In other embodiments, when a network device issues a save command afterthe data edited in step 500, instead of being stored to the stub filelocation, the data may be stored back to the archive location, leavingthe stub file intact, except that if the stub file may keep track ofdata information, such information may be changed according to theedited data.

In an embodiment that stores files that can be read by a network deviceusing the Windows operating system, for example, the data migrator mayproduce a Windows shortcut file of the same name as the archived file.Other operating systems may provide for use of shortcut files similar toWindows shortcuts that can be used as stub files in the present system,including, for example, Mac OS by Apple Computer, Inc. of Cupertino,Calif.

Also, in embodiments which store files that can be read by a networkdevice using Unix type file systems, such as Linux, Solaris, or thelike, a softlink is used for re-direction, which is similar to a Windowsshortcut. For example, a typical command to create a softlink in Unixsystems is as follows: [0054] In-s/primary_storage_location/stubfile/secondary_storage_location/archivefilewherein primary_storage_location is the location in the primary storagedevice, the stubfile is the name of the stub file containing thesoftlink, the secondary_storage_location is the location to which thefile is archived, and the archivefile is the name of the file stored inthe secondary location.

In some Unix-based systems, such as Solaris, when a network device needsto read a file, the network directory and drive where the file residesmay need to be mounted if the directory and file are not alreadymounted. When the network device issues a read request to a NAS deviceto read an archived file in such a system, the Softlink stored in thedata's primary storage location may have been archived to a drive ordirectory that is not already mounted for file access.

One way to resolve this issue of unmounted drives or directories is totrap the read request, either by the NAS device or the network device,to interrupt processing and to mount the drive and/or directory to whichthe Softlink is pointing to the archived data so the network device maythen read the data from the secondary location.

However, many Unix file systems do not provide a ready infrastructure totrap an input/output request before the request is usually propagated tothe file system. Using Solaris as an example, many Unix systemstypically provide a generic file system interface called a virtual filesystem (vfs). Vfs supports use by various file systems such as the Unixfile system (ufs), Unix network file system (nfs), the Veritas filesystem (vxfs), etc. Similarly, directories in these file systems mayneed to be mounted on the individual network devices in Unix basedsystems. Vfs can act as a bridge to communicate with different filesystems using a stackable file system.

FIG. 6 is a flow chart illustrating some of the steps performed in aSolaris-based embodiment of the present invention, which provides one ormore data migrators that each which may include a stackable loopbackfile system. The stackable loopback file system's interface may bedesigned such that if a network device or an application issues aread/write request (i.e., an open( ) request), the stackable loopbackfile system intercepts the request (step 600). The stackable loopbackfile system may provide a facility to trap calls, such as open, read,write and other typical Unix file operations if the request is for astub file (step 602). If the request is for a non-archived file, (step604) then the stackable loopback file system propagates the normaloperations to the underlying file system such as ufs and vxfs, step 605,and a regular open( ) is performed by the underlying file system.

Otherwise, if the request is for an archived file, FIG. 6 presents someoptions of three different embodiments to perform the handling of thetrapped request, steps 606A, 606B or 606C, after which, the system mayredirect the application or restores the file stored at the secondarylocation to the stub file location, step 608. Option one, step 606A, isto override the open( ) operation in the libc.so library with a newopen( ) command (i.e. cv_open). This may be used for applications thatuse libc.so during runtime. For the applications which are usingdynamically linkable libraries, if the open( ) operation can beoverwritten in libc.so with cv_open keeping intact the existing symbolsfor the other calls, then this option will work for those applicationsas well. However, this option may not work for applications whichdirectly open the file in the kernel, such as database applications.Further, this option may not work for the statically linkedapplications.

Option two, step 606B, involves changing the trap handler for the open() system call. Trap handlers are implemented in assembly and aretypically specific to the various Unix architectures. Solaris systemsusually include a generic trap handler for system calls and other trapsand may be implemented, if desired.

Option three, step 606C, may be used for implementing a stackableloopback file system. This option uses a loopback file system thatpropagates the normal operations to the underlying file System like ufs,vxfs and also provides a facility to trap the required calls. Thestackable loopback file system provides the various vfs operations. Thestackable loopback file system also provides vnode operations typicallyused by other file systems. A vnode may be a virtual node comprising adata structure used within Unix-based operating systems to represent anopen file, directory, device, or other entity (e.g., socket) that canappear in the file system name-space. The stackable loopback file systemprovides a mount option to mount the existing file directory to someother location that is used as the secondary location for storing thefile. The special mount operation may search through the underlying filesystem, store the necessary information of the underlying file system,and assign the path as its starting root. Example commands to accomplishthis operation follows:

mount_cxfs/etc/etc

mount_cxfs/etc/tmp/etc_temp

Where /etc/tmp/etc_temp does not appear in a mounted path already. Thismount option is used for those file directories, which are not alreadymounted.

One way to implement the additional functionality of stackable loopbackfile system is to make the stackable loopback file system a loadablemodule or driver. Unix systems, such as Solaris, usually support filesystem drivers such as the loadable modules. The stackable loopback filesystem module may support both normal file system and driverfunctionalities. The stackable loopback file system driver may useinput-output controls (ioctls), which are special request device driversabove and beyond calls to the read or write entry points, to provide thecapability to mount the file directories. Vnode operations may simplypass through the driver to the underlying file system, except thatread/write/mmap operations are trapped to handle data migration of therelocated files, and performs a lookup operation to resolve recursionsof the files mounted to some other location.

The driver may be included in the migrator, preferably in an embodimentwhere the migrator resides on the NAS. The migrator may include arelocate daemon that triggers the data migration for the files to bemigrated if user defined policies are met. The relocate daemon may thencreates the stub file. A redirect/restore daemon may be triggered by thestackable loopback file system when a stub file is accessed. The restoredaemon may mount the drive and/or secondary drive or directory where thefile was archived if the drive and directory are not already mounted.The stackable loopback file system may then re-directs the networkdevice to the directory where the file is stored as described above. Inan alternative embodiment, after mounting the drive and directory, thefile may be restored to the primary location. The driver may generate anevent for the restore daemon to complete restoration. Restore daemon maysend an ioctl for the completion of the restoration and deletes the stubfile.

Thus, as can be seen from the above, systems and methods for recoveringelectronic information from a storage medium are provided. It will beunderstood that the foregoing is merely illustrative of the principlesof the present invention and that various modifications can be made bythose skilled in the art without departing from the scope and spirit ofthe invention. Accordingly, such embodiments will be recognized aswithin the scope of the present invention.

Systems and modules described herein may comprise software, firmware,hardware, or any combination(s) of software, firmware, or hardwaresuitable for the purposes described herein. Software and other modulesmay reside on servers, workstations, personal computers, computerizedtablets, PDAs, and other devices suitable for the purposes describedherein. Software and other modules may be accessible via local memory,via a network, via a browser or other application in an ASP context, orvia other means suitable for the purposes described herein. Datastructures described herein may comprise computer files, variables,programming arrays, programming structures, or any electronicinformation storage schemes or methods, or any combinations thereof,suitable for the purposes described herein. User interface elementsdescribed herein may comprise elements from graphical user interfaces,command line interfaces, and other interfaces suitable for the purposesdescribed herein. Screenshots presented and described herein can bedisplayed differently as known in the art to input, access, change,manipulate, modify, alter, and work with information.

While the invention has been described and illustrated in connectionwith preferred embodiments, many variations and modifications as will beevident to those skilled in this art may be made without departing fromthe spirit and scope of the invention, and the invention is thus not tobe limited to the precise details of methodology or construction setforth above as such variations and modification are intended to beincluded within the scope of the invention.

Persons skilled in the art will appreciate that the present inventioncan be practiced by other than the described embodiments, which arepresented for purposes of illustration rather than of limitation andthat the present invention is limited only by the claims that follow.

While the invention has been described and illustrated in connectionwith preferred embodiments, many variations and modifications as will beevident to those skilled in this art may be made without departing fromthe spirit and scope of the invention, and the invention is thus not tobe limited to the precise details of methodology or construction setforth above as such variations and modification are intended to beincluded within the scope of the invention.

What is claimed is:
 1. A method for managing the storage of electronicdata, the method comprising: storing a first copy of files at a firststorage location associated with a network storage device (“NASdevice”), wherein the NAS device has an internal operating system and aninternal file management system, and wherein the NAS device communicateswith other devices via a network; tracking the first copy of the filesstored in the NAS device with a data migrator that is external to theNAS device, wherein the data migrator executes on one or more computerprocessors that are externally located from the NAS device, wherein thedata migrator also has a different file management system than the NASdevice and maintains index data in a location external to the NAS devicethat comprises information about the first storage location associatedwith the NAS device; processing at least one storage policy with thedata migrator to determine when to copy the first copy of the files onthe NAS device to one or more secondary storage devices; using the indexdata to identify that the first copy of the files is stored in the firststorage location associated with the NAS device; and migrating, with thedata migrator, the first copy of the files stored in the first storagelocation associated with the NAS device to a second storage location inone or more secondary storage devices externally located from the NASdevice.
 2. The method of claim 1, wherein migrating the first copycomprises compressing or otherwise encoding at least a portion of thefirst copy.
 3. The method of claim 1, further comprising, in response toa request to access data stored in the first storage location, directlyretrieving data stored in the one or more secondary storage devices. 4.The method of claim 3, further comprising decompressing or otherwisedecoding the retrieved data.
 5. The method of claim 4, whereindecompressing the retrieved data creates substantially the same formatthe retrieved data was in prior to storage in the second storagelocation.
 6. The method of claim 1, further comprising automaticallyreplacing, with the data migrator, the first copy of the files stored inthe NAS device with a stub that identifies the second storage location.7. The method of claim 6, further comprising storing edits to the filesin the first storage location by replacing the stub with the editeddata.
 8. The method of claim 6, further comprising storing edits made tothe files in the one or more secondary files and changing the stub fileaccording to the edits.
 9. The method of claim 1, wherein the index dataindicates a logical association between the second storage location anda media agent configured to transfer data to the second storagelocation.
 10. A system for managing the storage of electronic data, thesystem comprising: a network storage device (“NAS device”) that stores afirst copy of files at a first storage location associated with the NASdevice, wherein the NAS device has an internal operating system and aninternal file management system, and wherein the NAS device communicateswith other devices via a network; index data stored in a locationexternal to the NAS device, the index data including information aboutthe first storage location; and a data migrator executing in one or morecomputer processors, wherein the data migrator is externally locatedwith respect to the NAS device and has a different file managementsystem than the NAS device, wherein the data migrator maintains theindex data, and wherein the data migrator is further configured to:track the first copy of the files stored in the first storage locationassociated with the NAS device; process at least one storage policy todetermine when to copy the first copy of the files in the first locationassociated with the NAS device to a second storage location in asecondary storage device externally located from the NAS device; use theindex data to determine that the first copy of the files is stored inthe first storage location associated with the NAS device; and migratethe first copy of the files from the first location to the secondlocation.
 11. The system of claim 10, wherein the data migrator isfurther configured to automatically replace the first copy of the filesstored in the NAS device with a stub that identifies the secondlocation.
 12. The system of claim 11, wherein the data migrator isfurther configured to store edits to the files in the first storagelocation by replacing the stub with the edited data.
 13. The system ofclaim 11, wherein the data migrator is further configured to store editsmade to the files in the second location without transferring the editsto the first storage location while leaving the stub file intact. 14.The system of claim 10, wherein the data migratory is further configuredto retrieve data from the second storage location.
 15. The system ofclaim 14, wherein the data migrator is further configured to decompressor otherwise decode retrieved data from the second storage location. 16.The system of claim 11, wherein the stub file includes a UNIX softlink.